This application claims priority under a prior copending application filed in Belgium on Mar. 24, 1993, Application No. 09300288, which application is incorporated herein by reference in its entirety.
The present invention relates to self-adhesive bituminous compositions modified with polymers and generally used for manufacturing watertight roofing shingles. More particularly, the present invention relates to bituminous self-adhesive compositions having improved properties particularly advantageous for cold applications and offering rapid adhesion, resistance to peeling and desirable ring-and-ball temperature (RBT).
Also, the present invention involves watertight shingles having at least one layer of the inventive bituminous composition which composition utilizes bitumen, polymers, and mineral loads.
In some instances they might also contain other bituminous layers or modified bitumen. The bituminous compositions disclosed herein can also contain mineral or synthetic fibres and thixotropic agents such as silica.
It is well known to use bituminous compositions for manufacturing watertight shingles generally for roof covering. Traditional systems for making these products involve a process of warming up bitumen or flame soldering. It is obvious that this type of technique is dangerous considering the risk of fire caused by the utilization of a torch and other similar equipment.
One solution to eliminate the fire element is to use glues to avoid the fire danger, but such glues generally contain solvents that are not desirable from an environmental point of view. The result is also not successful each and every time.
Self-adhesive compositions comprising one linear styrene-butadiene-styrene tri-block copolymer and styrene-butadiene di-block copolymer are also known; however, these compositions require the use of mineral oil during application, and their properties are not acceptable from RBT and flow resistance points of view. The presence of oil can also increase the exudation risk.
There is therefore a need for improved bituminous self-adhesive cold-application compositions that present the following improved properties:
rapid adhesion
resistance to peeling
high ring-and-ball temperature
good obsolescence resistance
good elastic properties at low temperatures.
A bituminous self-adhesive cold-application composition responding to the criteria mentioned above is then the object of the present invention.
The present invention provides a bituminous self-adhesive cold-application composition that comprises a mixture of bitumen, a mixture of different thermoplastic polymers and tackifying resins, mineral loads, and optionally, fibres and/or thixotropic agents.
The present invention also teaches watertight roofing panels having at least one bituminous self-adhesive cold-application layer of the inventive composition.
The present invention also discloses a process for manufacturing the watertight panels.
Bituminous self-adhesive cold compositions of the present invention are characterized in that they comprise a mixture consisting of:
5 to 25% of a mixture of rubbery polymers of styrene-diene type comprising at least:
(a) radial styrene-butadiene block copolymer;
(b) linear and/or radial styrene-isoprene block copolymer; and
(c) styrene-diene di-block copolymer, preferably of statistical interlinking (xe2x80x9cstatistical intermediate sequencexe2x80x9d);
0 to 25% of one or more tackifying resins; and
5 to 95% bitumen.
The bituminous composition of this invention may also contain the usual mineral loads, including mineral or synthetic fibres, as well as thixotropic agents. These loads are generally used at the rate of about 0 to 40%, based on the weight of the bituminous composition.
It has now been found unexpectedly that such a bituminous self-adhesive cold-application composition meets not only all required properties from the point of view of cold adhesion, obsolescence, ring-and-ball temperature and cold elasticity, but also that the properties of the composition remain satisfactory even when one or more polymers are added. Furthermore, generally improved properties are obtained when at least three polymers are present. Thus, the bituminous composition of the invention comprises, in addition to tackifying resins and bitumen that will be described later, a mixture of different polymers selected from (A), (B) and (C) described in detail below:
(A) Radial styrene-butadiene block copolymer with a styrene content of approximately 15 to 45 weight percent and preferably in the range of 25-35 weight percent, and a weight-average molecular weight (Mw) between 100,000 and 600,000, and preferably in the range of 250,000 to 350,000. The copolymer (A) preferably represents between 10 and 45 weight percent of the total polymeric mixture and more preferably between 15 and 35 weight percent of the polymeric mixture.
(B) Linear and/or radial styrene-isoprene in which the styrene component represents from 10 to 40 weight percent and preferably from 10 to 20 weight percent and in which the total molecular weight is between 60,000 and 400,000, preferably between 100,000 and 150,000.
Examples of appropriate linear and radial copolymers would be coupled styrene-isoprene and styrene-isoprene-styrene. The copolymer (B) preferably represents between 5 and 50 weight percent of the polymeric mixture and more preferably between 5 and 25 weight percent of the polymeric mixture.
(C) Styrene-diene di-block copolymer, preferably styrene-butadiene in which the styrene portion represents from about 15 to 45 weight percent and preferably from about 20 to 35 weight percent and whose total molecular weight is between 50,000 and 150,000, and preferably between 50,000 and 100,000. Preferably, copolymer (C) used in the present invention is of the type utilizing statistical interlinking which means that it contains one styrene block and one styrene-butadiene block in a statistical distribution. Generally, the styrene block represents about 70% of the total styrene. Copolymer (C) is used simultaneously as a compatibility agent and an adhesive. Copolymer (C) preferably represents approximately 10 to 75 weight percent of the polymeric mixture and more preferably from 30 to 60 weight percent.
Styrene-conjugated diene block copolymers appropriate for the present invention also include their partially and totally hydrogenated derivatives.
The bituminous composition of the invention may also contain one or more tackifying resins at the rate of from about 0 to about 25 weight percent of the total bituminous composition. Higher quantities can be used but to the detriment of some properties. The role of tackifying resins is well known in the sector of adhesives.
The tackifying resins are well known conventionally and are more particularly described in U.S. Pat. No. 4,738,884, which is incorporated herein by reference in its entirety.
The bitumen useful in the present invention can be direct distillation bitumen or oxidized bitumen, natural bitumen, precipitation bitumen and others. It is also clear that different types of bitumen can be mixed as well as modified by addition of one or more oils.
According to the present invention, it is desirable to use a bitumen having a penetration index at 25xc2x0 C., of less than 800 (0.1 mm) (ASTM D 5-73 norm), and preferably between 30 and 400. Direct distillation bitumen is preferable, with a preference for one which has a penetration index between 80 and 250.
It has been unexpectedly found that the combination of the three copolymers (A), (B) and (C) allows the preparation of bituminous compositions that have improved properties, especially cold adhesion, at the same time keeping good ring-and-ball temperature (RBT) and elongation and elasticity properties when cold.
In fact, it was noted that when one or more polymers (A), (B) and (C) were not present in the formulation, the obtained properties were not as good.
It has also been found that according to a particular method of execution of the present invention it is possible to introduce advantageously one linear styrene-butadiene block copolymer into the rubbery polymers mixture.
The block copolymers (A), (B) and (C) are well known in the polymer field. They are generally obtained during anionic polymerization of monomer feeds in a solvent in the presence of an alkylmetallic catalyst such as alkyllithium. They can be prepares during successive polymerization of styrene and butadiene or isoprene when linear block copolymers are involved. In case radial structure block copolymers are involved, copolymers able to exhibit at least three branches are utilized, with every branch having at least one polystyrene block and one polybutadiene or polyisoprene block. This method is described in U.S. Pat. No. 3,281,383, which is incorporated by reference herein in its entirety. The above described copolymers can comprise statistical parts and be within the scope of the present invention. Copolymers do not have to be necessarily of a symmetric composition. All molecular weights referred to in this disclosure are weight-average molecular weights (Mw).
The present invention also discloses watertight roofing panels which comprise at least one cold-application self-adhesive layer made according to the above described bituminous composition and one or more optional bituminous layers modified with polymers and possibly with added mineral loads. However, it is entirely unexpected and it is a great advantage of the inventive compositions that they can constitute the entire watertight panelling, even though it was necessary to use other layers in conventional roofing compositions to guarantee required thermo-mechanical properties (e.g. RBT) and for providing a non-adhesive layer comprising bitumen modified with a rubbery polymer, and mineral loads and other thixotropic agents. Thus, the present invention eliminates this need for additional non-adhesive layers of bitumen, rubbery polymer modified bitumen, and bitumen loaded with minerals and thixotropic agents.
The compositions of the present invention present a great advantage over conventional techniques since they not only exhibit improved properties but can also be used in the form of sole composition sheets.
The bituminous self-adhesive cold-application compositions of the present invention can also be used for other purposes such as mastics, emulsions or other watertight sealants.